Bitcoin.io, in my opinion,is a REAL SCAM. I faced the same situation. After my balance accumulated to more than .005 bitcoin, I tried to withdraw and got their standard reply stating: "Hello! BitMiner has detected couple accounts on your ip, but there can only be one V1.0 active. This can be caused by VPN or another PC on your network. Sorry but you cant have couple free V1.0 accounts as stated in BitMiner FAQ. Similar accounts can not be deleted. You can solve this problem by upgrading BitMiner. Upgraded versions have no such limitations. Date: 2017-08-25 05:46:41 "
Then I sent more support tickets stating that I never opened a second account and demanded my withdrawal amount. All the time I got the same answer and then once I got this reply:  "Hello! System tells us another account 18VcVHiULBuwex7vqYAaBq1XBsxoDqu2A7 uses same ip. This can be caused by VPN or another PC on your network. Similar accounts can not be deleted. You can solve this problem by upgrading BitMiner. Upgraded versions have no such limitations. Date: 2017-08-25 15:53:22"
The same account number had been mentioned by them as a standard reply to few other members, which I saw here in other posts.
Then I sent few more support tickets and got their same standard replies. And lastly, I sent them this message: "Please refer to my previous Support Ticket with Ticket PIN: CC0E0DC Category: Withdrawal questions. Are you as sick like a PARROT ? You are able to repeat the words (your answers), but you do not understand its meaning. Give me a single proper justifiable answer. Are you really a STUPID person ? You CHEATER & A LIAR? SHUT YOUR MOUTH & STOP PARROTING. OTHERWISE YOU MIGHT LOSE YOUR TONGUE ONE DAY. Date: 2017-08-26 21:32:15"
Taking into account all the above events, I'm sure that this is really a SCAM website. My advice to people who are planning to deal with this website: DON'T JOIN BITCOIN.IO & NEVER UPGRADE. OTHERWISE YOU'LL DEFINITELY LOSE YOUR HARD EARNED MONEY AND BECOME ANOTHER VICTIM OF A PONZI SCHEME.